Plastic printing plate and method



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v PLASTICv mmm: mm 'um lemon 4Fuga oct. s, 1945 21 f INvENToR mm l. BILLY www HTTORNEY Patented June 26, 1951 PLASTIC PRINTING PLATE AND METHOD Edward H. Reilly, Westport, Conn., assigner to Electrographic Corporation, New York, N. Y., a corporation of Delaware Application October 3, 1945, Serial N o. 620,117

1 claim. l

The present invention relates to a novel and improved printing member and to a process of forming the same.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious'herefrom, or may be learned by practice with the invention. the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claim.

The invention consists in the novel parts. constructions, arrangements, combinations and improvements herein shown and described.

The accompanying drawings, referred to herein and constituting a part hereof, illustrate one embodiment of the invention, and together with the description, serve to explain the principles of the invention.

Of the drawings:

Figure 1 is a schematic view of a step in the process of forming a printing plate in accordance with the present invention:

Figure 2 is a cross-sectional view of a typical and illustrative printing plate being formed in accordance with the present invention, the surface of said plate being exaggerated; and

Figure 3 is a view of a completed printing member in accordance with the invention, ready for mounting on a printing cylinder.

'I'he present invention has for its object the provision of an improved printing member forv rotary letterpress printing. A further object is the provision of a printing member which can be operated at higher printing speeds, has extremely long life and can be rapidly and economically produced.

Referring now in detail to the accompanying drawings which illustrate a preferred process of forming the printing plate in accordance with the present invention, there is provided a mold' or matrix I of the printing plate to be reproduced, which matrix is preferably formed of metal or a thermally set phenolformaldehyde resin. The matrix I0 is covered with a quantity of a powdered plastic material which is thermoplastic, somewhat resilient, chemically and physically unaffected to any substantial degree by the ink to be used in printing or by the solvents used for cleaning the printing plates, has a high degree of resistance to abrasion and is not greatly aiected by changes in humidity nor press-operating temperatures. For this purpose, I have found that the vinyl resins. particularly the unfilled copolymer of vinyl chloride and vinyl acetate are surprisingly eective. In addition, such vinyl resins are reasonably economical, can

2 i be rapidly molded and can be remelted for repeated use.

The preferred material for my printing surface II is the transparent vinyl resin sold under the trade name of Vinylite 50. The layer of this transparent resin Ii is preferably about 2 or 3 tenths of an inch and is levelled prior to further treatment.

On top of the layer II is placed one or more thin sheets I2 of vinyl resin, such as the vinyl copolymer of the chloride and acetate mixed with filler, such as carbon, rendering it less resilient than the unlled layer II used for the printing surface. The backing layers I2 are preferably about one or two tenths of an inch in thickness.

The matrix I0 with the layers II and I2 thereon is then placed on the lower platen I5 of a heated hydraulic press. Bars I6 are placed around the matrix I0 and slightly spaced therefrom, so that the composite printing plate will be molded to the proper thickness. When the A matrix I0 and resin layers l I and I2 have reached the proper temperature, which may be accelerated by using mildly preheated powdered and sheet vinyl resins, the upper heated platen Il is brpught against the work and the matrix and resin are subjected to molding pressure, of many tons, often as much as from fifty to one hundred tons. the temperature of the platens being suitably adjusted from 210 F. to 240 F. depending on the resin being molded and the time allowed for the molding.

'I'he powdered resin II used for the face of the plate permits it to flow faster and more accurately into the recesses and configurations of the mold surface, while its transparency due to its unfilled character, reveals imperfect molding more easily at the same time as providing a more durable, more elastic and resilient surface than would be provided by the filled resin.

When molding is complete, the upper platen I 1 is raised and the matrix and the molded plate I8 thereon is removed. Excess resin has owed into the space between the matrix and bars I6. The printing plate I8 is removed from the rmatrix I0 and is then trimmed to the desired size after which it may be allowed to cool. If desired, the plate may then be proved in the at state.

For use.`there is provided a parti-cylindrical member 20, the inner surface of which conforms to the outer surface of the plate cylinder on which the member 20 is to be mounted. The member 20 is preferably almost semi-cylindrical having a driving edge 2I to llt against the driving stop on the plate cylinder, and a bevel edge 3 22 to be engaged by plate clamps. The member 20 is preferably formed of a light alloy having good compressive strength, such as duraluminum. and is generally about inch in thickness.

The outer surface of member 20 is also particylindrical and provides a true base on which the printing plates may be secured in proper, accurately registered relation.

Figure 2 shows a fragmentary cross sectional view of a printing plate i8, while Figure 3 shows the curved member 20 on which two plates I8 have been secured, ready for printing.

The completed, trimmed and proved plate I8 is heated to a temperature of 150 F. to 200 F. to render it more flexible, its back is then coated with some suitable adhesive, such as that disclosed in the patent to Edgar, 2,064,802 of 1936. While the plate IB is still flexible and warm, it is pressed onto and accurately positioned for register on the curved member 20 and is held there by pressure until the adhesive is fully set, thereby forming the printing member of Figure 3.

The finished printing member is advantageous as its mass is only about one-third that of the conventional stereotypeand it can be operated at higher speeds without danger or undue strain. The resilientl surface of the plate prevents excessive pressure from puncturing or indenting the paper, at the same time compensating for` inequalities in the impression or printing surface.

When printing has been completed, the backing member 2U may be heated and the printing plates I8 peeled therefrom, after which the resin from the plates i8 may be used again, for instance, to form the backing layers l2 of the next plates IB.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom 4 within -the scope of the accompanying claim without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

The process of forming a printing member comprising covering the surface of a matrix with a powdered, thermoplastic, unfilled and transparent vinyl resin, covering said unfilled vinyl resin with at least one sheet of a lled vinyl resin, the thickness of the lled vinyl resin section not to exceed the thickness of the unfilled vinyl resin section, said vinyl resins, when cured being ilexible, somewhat resilient, and abrasive resistant, molding said resins under pressure and at a temperature of from between about 210 F. to about 240 F. to integrally unite the two layers of vinyl resin, bending the formed printing plate while at a temperature of from between about F. to 180 F. and adhesively securing it to relatively thicker light-weight curved metal alloy member while the plate is warm and flexible and allowing it to set while pressed against said member.

EDWARD H. REILLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,377,509 Novotny May 10, 1921 1,803,548 Drake May 5, 1931 2,028,712 Swan Jan. 21, 1936 2,078,535 Hagedorn Apr. 27, 1937 2,108,822 Lippincott Feb. 22, 1938 2,248,275 Langel July 8, 1941 FOREIGN PATENTS Number Country Date 17,809` Australia Jan. 12, 1929 

